KR20240019883A - Brushless Motor - Google Patents

Abstract

The present invention relates to a brushless motor, and more specifically, to a motor that can minimize the distortion factor of the no-load back electromotive force of the motor and reduce torque ripple and cogging torque.

Description

Brushless Motor

The present invention relates to a brushless motor, and more specifically, to a motor that can minimize the distortion factor of the no-load back electromotive force of the motor and reduce torque ripple and cogging torque.

Recently, in accordance with the low-pollution, high-fuel-efficiency policy due to problems such as depletion of fossil fuels and environmental pollution, hybrid vehicles or electric vehicles that use both fossil fuels and electricity as driving sources have been in the spotlight, and research on them is being actively conducted.

Hybrid cars and electric cars obtain power to propel the vehicle through an electric motor. Accordingly, unlike the widespread use of mechanical compressors in existing vehicle air conditioning systems, there is a recent trend toward using electric compressors.

The electric compressor includes an electric motor that converts electrical energy into mechanical energy and an inverter that controls the rotation of the electric motor. The electric motor of such an electric compressor generally consists of a cylindrical rotor and a stator with a coil wound around its outer circumference, and is divided into distributed winding and concentrated winding depending on the coil winding method.

In such an electric compressor, the rotor included in the electric motor rotates as current flows through the coil by power supplied from the inverter, and the rotational force of the rotor is transmitted to the rotating shaft. And the mechanical means, which receives mechanical energy from the rotating shaft, compresses the refrigerant through reciprocating motion.

Electric compressors have the disadvantage of being inferior in refrigerant compression performance compared to existing mechanical compressors. This is because the driving force generated by an electric motor is weak compared to a mechanical compressor driven using the rotational force of an engine, vibration is severe, and the control performance of the inverter is poor. It was because of a problem that was not high. In addition, there was a problem that the electric motor was low in efficiency and the electricity supplied to the vehicle was wasted.

One of the many causes that cause vibration and reduce precision of electric motors is the cogging torque and torque ripple generated by the interaction between the permanent magnet and the slot, and the motor with the slot present. Cogging torque and torque ripple are bound to exist.

Cogging torque is a radial force that tries to move the motor system to a position where the magnetic energy of the motor system is minimum, that is, in an equilibrium state. It is a non-uniform torque generated by the interaction between the magnetic pole of the permanent magnet and the slot, regardless of the load current. , which has a significant impact on the control and precision of the motor.

In order to reduce this cogging torque, there is a known method of reducing the cogging torque by structurally appropriately combining the number of poles and the number of slots of the permanent magnet. However, in the field of electric motors used in compressors for hybrid vehicles, there are still not many specific research results regarding the optimal ratio of magnetic poles and the number of slots, or structures and designs that can reduce cogging torque and torque ripple. .

Figure 1 is a diagram showing a conventional electric compressor motor. The conventional electric compressor motor 3 has an internal resistance structure in which the rotor 4 rotates inside the stator 5, and the motor consists of 6 poles and 27 slots. , it has a distribution method in which the coils are widely distributed over several dimensions.

In the case of conventional electric compressors, the rotation speed is relatively low (about 10,000 rpm) and the load on the motor is high, so reduction of the weight and size of the motor is required. Multipolar design is necessary to reduce the weight and size of the motor. To achieve this, the electric motor must be designed in a way that increases the number of motor poles and reduces stacking, but as mentioned above, there are not many specific research results on this.

Korean Patent Publication No. 10-2018-0113296 (published on October 16, 2018)

The present invention was developed to solve the above problems, and provides design values for motor components and an optimized pole/slot combination that can minimize the distortion of the no-load back electromotive force of the motor and reduce torque ripple and cogging torque. There is a purpose to that.

The present invention is a brushless motor, comprising: a stator in which a plurality of winding slots are formed along the circumferential direction on the inner circumference of an axially hollow body; a rotor installed axially inside the stator and having a plurality of insertion grooves formed along the circumferential direction on the outer circumference; and a plurality of permanent magnets each inserted into the plurality of insertion grooves of the rotor, wherein a combination of the number of poles corresponding to the number of the plurality of permanent magnets and the number of slots corresponding to the number of the plurality of winding slots is used. Alternatively, cogging torque and torque ripple can be reduced.

The motor according to an example of the present invention may have a 10-pole, 24-slot structure in which the plurality of permanent magnets are composed of 10 and the plurality of winding slots are composed of 24.

If the radial length of the stator is Rs and the radial length of the rotor is Rr, the ratio (Rr/Rs) of the radial length (Rr) of the rotor to the radial length (Rs) of the stator is 0.594 ≤ Rr/Rs ≤ 0.646 can be satisfied.

If the arc angle formed between the center of the rotor and both ends of one of the plurality of permanent magnets is α, the arc angle (α) may satisfy 28° ≤ α ≤ 32°.

If the shortest distance from the center of the rotor to any one of the plurality of permanent magnets is Rm, the ratio (Rm/Rr) of the radius length (Rr) of the rotor to the shortest distance (Rm) is 0.847 ≤ Rm/Rr ≤ 0.898 can be satisfied.

The rotor is formed with a plurality of hollow holes penetrating the rotor in the axial direction, and the hollow holes may be composed of 10 corresponding to the plurality of permanent magnets.

The rotor is formed with a plurality of rivet holes through which rivets are inserted through the rotor in the axial direction, and the number of rivet holes may be formed between adjacent hollow holes, so that there are 10 rivet holes.

A motor according to another example of the present invention may have a 10-pole, 12-slot structure in which the plurality of permanent magnets are composed of 10 and the plurality of winding slots are composed of 12.

A pole shoe is formed at the tip of each of the plurality of stator teeth forming the plurality of winding slots, and the opposing surface of the pole shoe facing the outer peripheral surface of the rotor has a predetermined curvature, and the radial direction of the opposing surface of the pole shoe is The curvature at the center and the curvature at the radial ends may be different.

If the radius of curvature at one point of the opposing surface of the pole shoe is Rs_In, the radius of curvature (Rs_In) of the opposing surface of the pole shoe may satisfy 30 mm ≤ Rs_in ≤ 120 mm.

The minimum thickness of the pole shoe may be 0.8 mm or more.

The radius of curvature of the radial center of the opposing surface of the pole shoe is 30 mm, and the radius of curvature of the radial end of the opposing surface of the pole shoe is 120 mm. The radius of curvature gradually increases as it progresses from the center of the opposing surface of the pole shoe to the end. can do.

The thickness of the pole shoe at the radial end of the opposing surface of the pole shoe may be 0.8 mm.

The pole shoe may have a mirror symmetrical shape with respect to the radial center of the pole shoe.

A motor according to another example of the present invention may have a 10-pole, 27-slot structure in which the plurality of permanent magnets are composed of 10 and the plurality of winding slots are composed of 27.

If the radial length of the stator is Rs and the radial length of the rotor is Rr, the ratio (Rr/Rs) of the radial length (Rr) of the rotor to the radial length (Rs) of the stator is 0.520 ≤ Rr/Rs ≤ 0.646 can be satisfied.

If the arc angle formed between the center of the rotor and both ends of one of the plurality of permanent magnets is α, the arc angle (α) may satisfy 29° ≤ α ≤ 32°.

If the distance between two adjacent insertion grooves among the plurality of insertion grooves is referred to as the web thickness (WD), the web thickness (WD) may satisfy 1.6 mm ≤ WD ≤ 2.2 mm.

According to the present invention, by providing various combinations of the number of poles and the number of slots, and providing optimal values accordingly, the distortion factor of the no-load back electromotive force of the motor can be minimized, and the torque ripple and cogging torque are reduced through the optimal design of the permanent magnet. This can result in reduced motor vibration and noise.

Figure 1 is a diagram showing a conventional electric compressor motor.
Figure 2 is a cross-sectional view of a motor according to the first embodiment of the present invention.
Figure 3 is a cross-sectional view of the stator and rotor.
Figure 4 is a diagram for explaining web thickness and bridge thickness.
Figure 5 is a graph showing the efficiency characteristics of the motor according to web thickness.
Figure 6 is a graph showing the efficiency characteristics of the motor according to the bridge thickness.
Figure 7 is a diagram for explaining design variables of a motor.
Figure 8 is a graph showing torque ripple characteristics according to the ratio of the radius length of the rotor to the radius length of the stator.
Figure 9 is a graph showing the efficiency of the motor and the distortion rate characteristics of the back electromotive force according to the size of the arc angle.
Figure 10 is a graph showing torque ripple characteristics according to the radius length of the rotor for the shortest distance to the permanent magnet.
11 and 12 are cross-sectional views of a motor according to a second embodiment of the present invention.
Figure 13 is a diagram comparing a conventional motor and the motor of the present invention.
Figure 14 is a diagram for explaining a pole shoe according to an example of the present invention.
Figure 15 is a graph comparing the cogging torque of a conventional motor and a motor of the present invention.
Figure 16 is a graph comparing the load torque of the conventional motor and the motor of the present invention.
Figure 17 is a cross-sectional view of a motor according to a third embodiment of the present invention.
Figure 18 is a diagram comparing a conventional motor and the motor of the present invention.
Figure 19 is a diagram to explain the design variables of the motor.
Figure 20 is a graph showing torque ripple characteristics according to the ratio of the radius length of the rotor to the radius length of the stator.
Figure 21 is a graph showing the efficiency of the motor and the distortion rate characteristics of the back electromotive force according to the size of the arc angle.

Hereinafter, the present invention will be described with reference to the attached drawings.

First, the motor of the present invention may be a brushless motor provided in an electric compressor for a vehicle. An electric compressor for a vehicle generally includes a compression unit in which the refrigerant is compressed by the reciprocating motion of the mechanical structure, an electric motor that transfers mechanical energy to the compression unit, and an inverter that supplies electrical energy to the electric motor, according to the present invention. The motor may correspond to an electric motor applied to such a general automotive electric compressor. Hereinafter, the motor of the present invention will be examined in detail through each embodiment.

<First Example>

First, the first embodiment of the present invention will be described. 2 to 10 are diagrams for explaining the motor of the first embodiment of the present invention.

Figure 2 is a cross-sectional view of a motor according to the first embodiment of the present invention, and Figure 3 is a cross-sectional view of a stator and a rotor. As shown, the motor 10 of the present invention includes a stator 100 and a rotor 200. It includes a plurality of permanent magnets (M) inserted into the rotor 200.

The stator 100 is formed in a substantially cylindrical shape and includes a body 110 that is hollow in the axial direction, and a plurality of winding slots 120 are formed along the circumferential direction on the hollow inner circumference of the body 110, each winding slot. A coil (C) is wound at (120). Each winding slot 120 is formed through the axial direction of the body and spaced apart from each other, and the coil C may be wound in a distributed manner widely distributed across several winding slots 120.

The rotor 200 is a cylindrical member installed axially inside the stator 100, that is, in the hollow of the body 110. The rotor 200 may have a plurality of permanent magnets combined so that it can rotate by receiving electromagnetic force generated as a current flows through the coil C wound on the stator 100. A plurality of insertion grooves 210 may be formed so that each of the plurality of permanent magnets can be inserted. Each insertion groove 210 is formed through the axial direction and is spaced apart from each other along the circumferential direction.

Meanwhile, a plurality of hollow holes 230 penetrating the rotor in the axial direction may be formed in the rotor 200 corresponding to the permanent magnets M, and a rivet hole 240 may be formed between adjacent hollow holes 230. Each can be formed. Like the hollow hole 230, the rivet hole 240 may have a structure that penetrates the inside of the rotor 200 in the axial direction, and a plurality of steel plates are inserted into the rivet hole 240 to form the rotor. This can be permanently combined. More specifically, as will be described later, the hollow holes 230 are composed of 10 corresponding to the number of permanent magnets (M), and the rivet holes 240 are formed between the hollow holes and can be composed of 10. This can help improve the flux characteristics by permanent magnets and the manufacturability of the rotor, and can reduce weight compared to conventional electric compressor motors.

A plurality of permanent magnets (M) are respectively inserted into the insertion grooves 210 in the axial direction, and permanent magnets (M) of different poles may be inserted into adjacent insertion grooves 210. That is, in the motor 10 of the present invention, the permanent magnet (M) is not attached to the surface of the rotor but is embedded inside the surface of the rotor, and in this case, magnetic torque (Magnetic Torque) is generated according to the arrangement of the magnetic field and the intensity of the magnetic field. Since reluctance torque (torque according to changes in magnetic resistance) can be used in addition to torque), the same torque can be generated using less current, increasing the efficiency of the motor.

At this time, the motor 10 of the present invention consists of 24 winding slots 120 and 10 permanent magnets (M), forming a 10-pole, 24-slot structure. That is, 24 winding slots 120 are formed in the stator 100, and the 24 winding slots are provided at regular intervals so that each winding slot forms an angle of about 13 degrees with the adjacent winding slot 120. In addition, 10 insertion grooves 210 are formed in the rotor 200, and the 10 insertion grooves are provided at regular intervals so that each insertion groove forms an angle of about 36 degrees with the adjacent insertion groove, and the insertion of this structure A plurality of permanent magnets (M) are respectively inserted into the groove 210 and formed to correspond to the structure of the insertion groove 210.

As the motor's no-load back electromotive force distortion (THD; Total Harmonic Distortion) approaches a sine wave, cogging torque and torque ripple during operation are reduced and the vibration and noise of the motor are reduced, so it is important to minimize the no-load back electromotive force distortion. The motor 10 of the present invention adopts a 10-pole, 24-slot structure. This 10-pole, 24-slot structure is a desirable structure for minimizing the distortion factor of the no-load back electromotive force, and is very advantageous in reducing cogging torque that generates noise during operation due to the pole/slot combination.

Specifically, as the thickness of the web increases, the efficiency of the motor increases, and as the thickness of the bridge increases, the efficiency of the motor decreases. Considering these together with the minimum thickness that can be manufactured for the motor, the permanent magnet By configuring (M) to 10, the efficiency and manufacturability of the motor can be maximized. Figure 4 is a diagram for explaining the web thickness and bridge thickness, Figure 5 is a graph showing the efficiency characteristics of the motor according to the web thickness, and Figure 6 is a graph showing the efficiency characteristics of the motor according to the bridge thickness, the present invention Considering the data and the size and thickness of the motor, configure 10 permanent magnets (M). At the same time, the present invention can minimize the distortion of the no-load back electromotive force by configuring 24 winding slots 120 corresponding to 10 permanent magnets (M), which is the optimal number of poles considering the switching frequency of the inverter.

In other words, by adopting a 10-pole, 24-slot structure, the motor of the present invention can minimize the distortion of the no-load back electromotive force and greatly reduce the cogging torque and torque ripple, thereby reducing the vibration and noise of the motor, and at the same time, improving the motor's Manufacturability can also be secured.

At this time, in order to minimize cogging torque and configure the no-load back electromotive force as a sinusoidal wave while maintaining high efficiency of the motor, an optimized design for the magnetic pole angle of the permanent magnet embedded in the rotor is required. Below, we will look in detail at the optimized design of a motor that satisfies this.

Figure 7 is a diagram to explain the design variables of the motor, including the center of the rotor (O), the arc angle (α), the radius length of the stator (Rs), the radius length of the rotor (Rr), and the shortest distance to the permanent magnet. Shows the distance (Rm). The arc angle (α) is the angle formed between the center of the rotor (O) and both ends of one of the plurality of permanent magnets (M), that is, the angle formed by both ends of each permanent magnet (M) with the center (O) of the rotor. means. The radius length (Rs) of the stator means the distance from the center (O) of the rotor to the outer peripheral surface of the stator (100). The radius length (Rr) of the rotor means the distance from the center of the rotor (O) to the outer peripheral surface of the rotor 200. The shortest distance to the permanent magnet (Rm) is the shortest distance from the center of the rotor (O) to any one of the plurality of permanent magnets (M), that is, the shortest distance between each permanent magnet (M) and the center of the rotor (O). means distance.

Figure 8 is a graph showing torque ripple characteristics according to the ratio of the radius length of the rotor to the radius texture of the stator. As shown, at rated load, there is a torque ripple of about 7.6% or less when the radius-length ratio (Rr/Rs) is in the range of 0.594 to 0.646, and when the length ratio (Rr/Rs) is in this range, the torque Ripple is minimized, thereby minimizing motor vibration and noise.

[Table 1]

Table 1 above is a table showing the graph of FIG. 8 as data. The torque ripple rapidly decreases starting from the length ratio (Rr/Rs) of 0.594, increases again starting from about 0.63, and increases again starting from 0.646. It can be seen that the torque ripple increases rapidly again. At this time, when the length ratio (Rr/Rs) is in the range of 0.594 to 0.646, the torque ripple has a range (①) of about 7.6% or less and 3.6% or more, and when the length ratio (Rr/Rs) is in the range of 0.618 to 0.646, the torque ripple is It has a range (②) of approximately 4.9% or less and 3.6% or more. That is, based on the above data analysis, the motor of the present invention has a ratio (Rr/Rs) of the radius length of the rotor (Rr) to the radius length of the stator (Rs) of 0.594 ≤ Rr/Rs ≤ 0.646. It can be configured to satisfy, and more preferably, the length ratio (Rr/Rs) can be configured to satisfy 0.618 ≤ Rr/Rs ≤ 0.646.

Figure 9 is a graph showing the efficiency of the motor and the distortion rate characteristics of the back electromotive force according to the size of the arc angle. As shown, it can be seen that the size of the arc angle (α) maintains an efficiency of about 95.23% or more in the range of 28° to 32° and is effective in reducing the distortion factor (THD) of back electromotive force.

[Table 2]

Table 2 above is a table showing the graph of FIG. 9 as data. As the size of the arc angle (α) increases, the efficiency of the motor increases linearly from 95.24% to 95.43% (①), while the arc angle (α) increases linearly. When the size of is between 28° and 32°, the distortion rate does not increase significantly from about 0.62% to 0.75% (②). Rather, when the size of the arc angle (α) is between 30° and 32°, the distortion rate is about 0.75% to 0.72%. It can be seen that it decreases by % (③). That is, based on the data analysis above, the motor of the present invention can be configured so that the arc angle (α) satisfies 28°≤α≤32°, and more preferably, the arc angle (α) The size of can be configured to satisfy 30°≤α≤32°.

Figure 10 is a graph showing torque ripple characteristics according to the radius length of the rotor for the shortest distance to the permanent magnet. As shown, there is a cogging torque of about 7% or less and a torque ripple of about 6% or less when the radius-length ratio (Rm/Rr) is in the range of 0.847 to 0.898, and the length ratio (Rm/Rr) is within that range. When equipped, torque ripple is minimized and vibration and noise of the motor can be minimized.

[Table 3]

Table 3 above is a table showing the graph of FIG. 10 as data. The torque ripple decreases rapidly starting from the length ratio (Rm/Rs) of 0.847, and increases again starting from about 0.865, but increases gently to 0.898. It can be seen that In that range, that is, the length ratio range of 0.847 to 0.898, the torque ripple ranges from about 5.5% to 3.6% (①), showing low torque ripple characteristics. When the length ratio (Rm/Rs) is in the range of 0.85 to 0.88, the torque ripple ranges from about 0.44% or less to 3.6% or more (②), so better torque ripple characteristics can be achieved.

And, as the length ratio (Rm/Rs) increases, the cogging torque increases linearly correspondingly. Specifically, when the length ratio (Rm/Rs) is in the range of 0.847 to 0.898, the cogging torque is about 0.007 Nm or more and 0.026 Nm or less. It has a range (③), showing low cogging torque characteristics. When the length ratio (Rm/Rs) is in the range of 0.85 to 0.88, the cogging torque has a range (④) of about 0.008 Nm to 0.022, and thus better cogging torque characteristics can be obtained.

In other words, based on the data analysis above, the motor of the present invention has a ratio (Rm/Rr) of the radius length (Rr) of the rotor to the shortest distance (Rm) to the permanent magnet of 0.847 ≤ Rm/Rr. It may be configured to satisfy ≤ 0.898, and more preferably, the length ratio (Rm/Rr) may be configured to satisfy 0.85 ≤ Rm/Rr ≤ 0.88.

In addition, each design variable described above is related to each other by the size, shape, and arrangement of each component that makes up the motor, and the relevant design variable is such that the range of each design variable is satisfied by considering the relationship between each design variable. Each of these can be implemented by overlapping within one motor, and in this case, the efficiency, torque ripple, and cogging torque characteristics of the motor can be improved to the maximum.

<Second Embodiment>

Next, a second embodiment of the present invention will be described. 11 to 16 are diagrams for explaining the motor of the second embodiment of the present invention. Content that overlaps with what was explained previously will be omitted.

11 and 12 are cross-sectional views of the motor of this example. The motor 10 of this example consists of 10 permanent magnets (M) and 12 plurality of winding slots 120, resulting in a 10-pole, 12-slot structure. have As it has a 10-pole, 12-slot structure, the cogging torque frequency is of the 60th order, which is advantageous in terms of improving vibration and noise of the motor compared to conventional motors.

In this example, the shape of the pole shoe is different from that of the pole shoe of a conventional motor. A plurality of stator teeth 130 forming a plurality of winding slots are formed on the stator, and a pole shoe 140 is formed at the tip of each of the plurality of stator teeth 130 and protrudes from each stator tooth in a predetermined radial direction.

At this time, if the opposing surface of the pole shoe 140 that faces the outer peripheral surface of the rotor 200 is referred to as the opposing surface 140A of the pole shoe, in the case of a conventional motor, the opposing surface 140A of the pole shoe is generally the opposing surface of the rotor 200. While the outer peripheral surface is formed with the same curvature as the outer peripheral surface of the rotor 200, in the present invention, the opposing surface 140A of the pole shoe has a predetermined curvature, but is not the same curvature as the outer peripheral surface of the rotor 200. The curvature at the radial center (c) of the opposing surface (140A) of the pole shoe is configured to be different from the curvature at the radial end (e).

Figure 13 is a diagram showing a comparison between a conventional motor and a motor of the present invention. As shown, in the conventional case, the opposing surface of the pole shoe is formed with a constant curvature, and at this time, the cogging torque is 126 mNm and the torque ripple is 465 mNm and 6.68%. There will be deviations. On the other hand, in the present invention, the opposing surface (140A) of the pole shoe is formed with a different curvature at the center and end, and at this time, the cogging torque is 44 mNm and the torque ripple has a deviation of 214 mNm and 3.19%, compared to the conventional one. It can be seen that cogging torque and torque ripple are significantly reduced.

Specifically, if the radius of curvature at one point of the opposing surface 140A of the pole shoe is Rs_in, the present invention can be configured so that the radius of curvature (Rs_in) of the opposing surface of the pole shoe satisfies 30 mm ≤ Rs_in ≤ 120 mm, and accordingly, The efficiency of the motor can be increased. In addition, it is desirable for the pole shoe to have a predetermined thickness or more, and accordingly, the present invention can be configured so that the minimum thickness of the pole shoe 140 satisfies 0.8 mm or more.

A more specific example that satisfies this is as follows. Figure 14 is a diagram for explaining a pole shoe according to an example of the present invention. As shown, the radius of curvature of the radial center (c) of the opposing surface (140A) of the pole shoe is 30 mm, and the opposing surface (140A) of the pole shoe The radius of curvature of the radial end (e) is 120 mm, and the radius of curvature may gradually increase as it progresses from the center (c) of the opposing surface (140A) of the pole shoe to the end (e), and the degree of increase is The radius of curvature may increase uniformly to be constant.

In addition, as the curvature of the opposing surface 140A of the pole shoe decreases, the radius of curvature (Rs_in) increases. At this time, since the minimum thickness of the pole shoe 140 must be satisfied as described above, the radius of curvature (Rs_in) is the maximum. The thickness at the radial end (e) of the opposing surface (140A) of the pole shoe may be 0.8 mm. And, as shown, the pole shoe 140 of the present invention may have a mirror symmetrical shape with respect to the radial center (c) of the pole shoe.

Figure 15 is a graph comparing the cogging torque of the conventional motor and the motor of the present invention. As shown, the conventional motor has a large cogging torque in the range of -0.06 to 0.06, while the present invention has a large cogging torque in the range of -0.02 to 0.02. It can be seen that the cogging torque is small.

Figure 16 is a graph comparing the load torque of the conventional motor and the motor of the present invention. As shown, the conventional motor has a large load torque in the range of 6.45 to 6.92, while the load torque of the present invention is in the range of 6.58 to 6.8. It can be seen that is formed small.

As seen above, according to this example, the motor has a 10-pole, 12-slot structure, and the radius of curvature of the opposing surface of the pole shoe is formed within 30 to 120 mm, and the radius of curvature increases as it progresses from the radial center of the pole shoe to the end. As it has a structure that gradually becomes larger, torque ripple during operation is minimized, which is effective in improving vibration and noise, and at the same time has the advantage of reducing the overall weight of the motor compared to conventional motors.

<Third Embodiment>

Next, a third embodiment of the present invention will be described. 17 to 21 are diagrams for explaining the motor of the third embodiment of the present invention. Content that overlaps with what was explained previously will be omitted.

Figure 17 is a cross-sectional view of a motor according to a third embodiment of the present invention. The motor 10 of this example consists of 10 permanent magnets (M) and 27 winding slots 120, resulting in 10 It has a 27-slot structure. Based on the cross-section of the motor, the influence of weight according to area change is relatively larger for electrical steel sheets than for permanent magnets. Therefore, in order to improve the cogging torque and performance of the motor and reduce weight, the area of the electrical steel sheets must be shaped as much as possible. needs to be optimized. For this purpose, the present invention adopts a 10-pole 27-slot structure.

In order to reduce weight while maintaining high efficiency of the motor, optimized design for the length of the permanent magnet embedded in the rotor and rotor back core design are required. For this purpose, this motor can be configured with 10 hollow holes and rivet holes in the rotor, each corresponding to a permanent magnet.

Figure 18 is a diagram showing a comparison between the conventional motor and the motor of the present invention. As shown, the conventional motor has an efficiency of 94.6%, a cogging torque of 0.027 Nm, and a rotor weight of 532g, whereas the motor of the present invention has a motor of the present invention. The efficiency is 94.7%, the cogging torque is 0.019, and the rotor weight is 374g. It can be seen that the efficiency of the motor is increased compared to the prior art, and at the same time, the cogging torque and rotor weight are significantly reduced.

The specific design figures for this example are as follows. Figure 19 is a diagram for explaining the design variables of the motor. In the motor of this example, the ratio (Rr/Rs) of the radius length of the rotor (Rr) to the radius length of the stator (Rs) is 0.520 ≤ Rr/Rs ≤ 0.646 is satisfied, the arc angle (α) satisfies 29° ≤ α ≤ 32°, and the web thickness (WD) satisfies 1.6mm ≤ WD ≤ 2.2mm. The thickness (WD) of the web may correspond to the gap between two adjacent insertion grooves among the plurality of insertion grooves 210. As each variable in the motor of this example is configured to satisfy these conditions, the efficiency of the motor can be increased and the cogging torque and rotor weight can be reduced, as seen above.

Figure 20 is a graph showing the torque ripple characteristics according to the ratio of the radius length of the rotor to the radius length of the stator. In the case of this motor, the ratio of the radius length (Rr) of the rotor to the radius length (Rs) of the stator ( Rr/Rs) has a range of 0.520 ≤ Rr/Rs ≤ 0.646, preferably 0.54 to 0.6, and it can be confirmed that the torque ripple is formed as small as about 10.8% in that range.

Figure 21 is a graph showing the efficiency of the motor and the distortion rate characteristics of the back electromotive force according to the size of the arc angle. In the case of this motor, the arc angle is in the range of 29° ≤ α ≤ 32°, and the efficiency of the motor in that range is about 95.1. It can be confirmed that the distortion factor (THD) of the no-load back electromotive force is formed as small as about 1.2% or less.

As seen above, according to this example, the motor has a 10-pole, 27-slot structure, and the ratio of the radius length of the rotor to the radius length of the stator, the arc angle, and the thickness of the web are design variables, and the corresponding As each design variable is limited to an appropriate range, vibration noise can be minimized by minimizing torque ripple, high motor efficiency can be provided, and back electromotive force THD can be effectively reduced.

Above, embodiments of the present invention have been described with reference to the attached drawings, but those skilled in the art will understand that the present invention can be implemented in other specific forms without changing the technical idea or essential features. You will understand that it exists. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

10: motor
100: stator
110: body
120: winding slot
130: stator teeth
140: pole shoes
200: rotor
210: Insertion groove
230: hollow hole
240: Rivet hole
C: coil
M: permanent magnet

Claims (18)

As a brushless motor,
A stator in which a plurality of winding slots are formed along the circumferential direction on the inner circumference of an axially hollow body;
a rotor installed axially inside the stator and having a plurality of insertion grooves formed along the circumferential direction on the outer circumference; and
It includes a plurality of permanent magnets each inserted into a plurality of insertion grooves of the rotor,
A motor capable of reducing cogging torque and torque ripple by varying the combination of the number of poles corresponding to the number of the plurality of permanent magnets and the number of slots corresponding to the number of the plurality of winding slots.
According to paragraph 1,
A motor comprising 10 permanent magnets and 24 winding slots, resulting in a 10-pole, 24-slot structure.
According to paragraph 2,
Let the radial length of the stator be Rs and the radial length of the rotor be Rr,
The ratio (Rr/Rs) of the radial length (Rr) of the rotor to the radial length (Rs) of the stator satisfies 0.594 ≤ Rr/Rs ≤ 0.646,
motor.
According to paragraph 3,
If the arc angle formed between the center of the rotor and both ends of one of the plurality of permanent magnets is α,
The arc angle (α) satisfies 28° ≤ α ≤ 32°,
motor.
According to clause 4,
If the shortest distance from the center of the rotor to any one of the plurality of permanent magnets is Rm,
The ratio (Rm/Rr) of the radial length (Rr) of the rotor to the shortest distance (Rm) satisfies 0.847 ≤ Rm/Rr ≤ 0.898,
motor.
According to clause 5,
The rotor is formed with a plurality of hollow holes penetrating the rotor in the axial direction,
The hollow holes are composed of 10 corresponding to the plurality of permanent magnets,
motor.
According to clause 6,
The rotor is formed with a plurality of rivet holes through which rivets are inserted through the rotor in the axial direction,
The rivet hole is formed between the adjacent hollow holes and consists of 10,
motor.
According to paragraph 1,
A motor comprising 10 permanent magnets and 12 winding slots, resulting in a 10-pole, 12-slot structure.
According to clause 8,
A pole shoe is formed at the tip of each of the plurality of stator teeth forming the plurality of winding slots,
The opposing surface of the pole shoe facing the outer peripheral surface of the rotor has a predetermined curvature,
The curvature at the radial center of the opposing surface of the pole shoe is different from the curvature at the radial end,
motor.
According to clause 9,
If the radius of curvature at one point of the opposing surface of the pole shoe is Rs_In,
The radius of curvature (Rs_In) of the opposing surface of the pole shoe satisfies 30mm ≤ Rs_in ≤ 120mm,
motor.
According to clause 10,
The minimum thickness of the pole shoe is 0.8 mm or more,
motor.
According to clause 11,
The radius of curvature of the radial center of the opposing surface of the pole shoe is 30 mm,
The radius of curvature of the radial end of the opposing surface of the pole shoe is 120 mm,
The radius of curvature gradually increases as it progresses from the center of the opposing surface of the pole shoe to the end,
motor.
According to clause 12,
The thickness of the pole shoe at the radial end of the opposing surface of the pole shoe is 0.8 mm,
motor.
According to clause 13,
The pole shoe has a mirror symmetrical shape with respect to the radial center of the pole shoe,
motor.
According to paragraph 1,
A motor comprising 10 permanent magnets and 27 winding slots, resulting in a 10-pole, 27-slot structure.
According to clause 15,
Let the radial length of the stator be Rs and the radial length of the rotor be Rr,
The ratio (Rr/Rs) of the radial length (Rr) of the rotor to the radial length (Rs) of the stator satisfies 0.520 ≤ Rr/Rs ≤ 0.646,
motor.
According to clause 16,
If the arc angle formed between the center of the rotor and both ends of any one of the plurality of permanent magnets is α,
The arc angle (α) satisfies 29° ≤ α ≤ 32°,
motor.
According to clause 17,
If the gap between two adjacent insertion grooves among the plurality of insertion grooves is referred to as the thickness of the web (WD),
The thickness (WD) of the web satisfies 1.6mm ≤ WD ≤ 2.2mm,
motor.